"Antediluvian monster", a Mosasaurus discovered in a Maastricht limestone quarry, 1770 (contemporary engraving) Today, the two groups are still commonly treated under the single heading herpetology. Laurenti was the first to formally use the term Reptilia for an expanded selection of reptiles and amphibians basically similar to that of Linnaeus. The terms reptile and amphibian were largely interchangeable, reptile (from Latin repere, 'to creep') being preferred by the French. Linnaeus, working from species-poor Sweden, where the common adder and grass snake are often found hunting in water, included all reptiles and amphibians in class "III – Amphibia" in his Systema Naturæ. In the 18th century, the reptiles were, from the outset of classification, grouped with the amphibians. In the 13th century the category of reptile was recognized in Europe as consisting of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, lizards, assorted amphibians, and worms", as recorded by Beauvais in his Mirror of Nature. See also: Skull roof Reptiles, from Nouveau Larousse Illustré, 1897–1904, notice the inclusion of amphibians (below the crocodiles) ![]() Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae, which can grow up to 17 mm (0.7 in) to the saltwater crocodile, Crocodylus porosus, which can reach over 6 m (19.7 ft) in length and weigh over 1,000 kg (2,200 lb). Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. ![]() As amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades – the fetus develops within the mother, using a (non-mammalian) placenta rather than contained in an eggshell. Unlike amphibians, reptiles do not have an aquatic larval stage. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Modern non-bird reptiles inhabit all the continents except Antarctica. In particular, the Cretaceous–Paleogene extinction event wiped out the pterosaurs, plesiosaurs, and all non-avian dinosaurs alongside many species of crocodyliforms, and squamates (e.g., mosasaurs). In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. Genetic and fossil data argues that the two largest lineages of reptiles, Archosauromorpha (crocodilians, birds, and kin) and Lepidosauromorpha (lizards, and kin), diverged near the end of the Permian period. The earliest known eureptile ("true reptile") was Hylonomus, a small and superficially lizard-like animal. ![]() The earliest known proto-reptiles originated around 312 million years ago during the Carboniferous period, having evolved from advanced reptiliomorph tetrapods which became increasingly adapted to life on dry land. Others prioritize the clade Sauropsida, which typically refers to all amniotes more closely related to modern reptiles than to mammals. Many cladistic systems therefore redefine Reptilia as a clade ( monophyletic group) including birds, though the precise definition of this clade varies between authors. Modern cladistic taxonomy regards that group as paraphyletic, since genetic and paleontological evidence has determined that birds (class Aves) are the living sister taxon to crocodilians, and are thus nested among reptiles from an evolutionary perspective. In Linnaean taxonomy, reptiles are gathered together under the class Reptilia ( / r ɛ p ˈ t ɪ l i ə/ rep- TIL-ee-ə), which corresponds to common usage. Reptiles have been subject to several conflicting taxonomic definitions. The study of the traditional reptile orders, customarily in combination with the study of modern amphibians, is called herpetology. As of May 2023, about 12,000 living species of reptiles are listed in the Reptile Database. Living reptiles comprise four orders: Testudines ( turtles), Crocodilia ( crocodilians), Squamata ( lizards and snakes), and Rhynchocephalia (the tuatara). Reptiles, in common parlance, are a group of tetrapods with an ectothermic ('cold-blooded') metabolism and amniotic development.
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